为响应“十九大”绿色环保精神，满足循环流化床机组超低排放需求，建立准确的NOx排放浓度机理控制模型对于设计循环流化床机组脱硝自动控制方法具有重大意义。从循环流化床锅炉燃烧机理切入，建立即燃碳模型，并将燃料氮分为挥发分氮与即燃碳氮2部分构建NOx炉内自生成模型；考虑CO和即燃碳对NOx的还原作用推导NOx自还原模型；构建选择性非催化还原脱硝模型，综合以上模型建立了适应深度调峰的循环流化床NOx排放模型。探究了机组深度调峰下运行参数与NOx排放浓度的关系以及与选择性非催化还原脱硝效率的影响因素。仿真验证试验表明建立的循环流化床NOx模型取得了较好仿真效果，稳态工况的模型计算值平均预测时间为114 s，与实测值的平均相对误差为2.50%；深度调峰下的模型计算值平均预测时间为126 s，与实测值的平均相对误差为5.42%。模型计算量较实测量提前2～3 min，具有一定预测效果。NOx排放浓度模型可为今后循环流化床机组适应深度调峰、快速变负荷以及超低排放研究提供参考。

In order to respond to the green environmental protection spirit of the 19th National Congress of the Communist Party of China and meet the ultra-low emission requirements of circulating fluidized bed units, it is of great significance to establish an accurate NOx emission concentration mechanism control model for the design of denitrification automatic control method of circulating fluidized bed units. Based on the combustion mechanism of circulating fluidized bed boiler, the model of immediate combustion carbon was established, and the fuel nitrogen was divided into volatile nitrogen and immediate combustion carbon nitrogen to construct the self-generation model of NOx in the furnace. The NOx self-reduction model was derived by considering the reduction effect of CO and immediate combustion carbon on NOx. A selective non-catalytic reduction denitrification model was constructed, and a circulating fluidized bed nitrogen oxide emission model suitable for deep peak shaving was established based on the above models. The relationship between operating parameters and NOx emission concentration under deep peak regulation and the influencing factors of selective non-catalytic reduction denitrification efficiency were explored. The simulation verification test shows that the established circulating fluidized bed NOx model has achieved good simulation results. The average prediction time of the model calculation value under steady-state conditions is 114 s, and the average relative error with the measured value is 2.50%. The average prediction time of the model under deep peak shaving is 126 s, and the average relative error between the calculated value and the measured value is 5.42%. The calculation of the model is 2 - 3 minutes earlier than the actual measurement, which has a certain prediction effect.The designed NOx emission concentration model in this paper can provide a reference for the future research of circulating fluidized bed units to adapt to deep peak regulation, rapid load change and ultra-low emission.

0 引言

1 CFB锅炉NOx排放建模机理

2 循环流化床脱硝模型

   2.1 即燃碳模型

   2.2 NOx自生成模型

   2.3 NOx自还原模型

   2.4 炉外SNCR脱硝模型

   2.5 NOx排放模型

3 仿真验证

   3.1 研究对象

   3.2 烟气氧含量模型验证

   3.3 机组稳态工况验证

   3.4 变负荷验证

4 结论